This invention relates to cells and components thereof employed in the electrolytic production of aluminum from a fused bath, both by electrowinning and electrorefining processes, and to the aluminum production processes employing such cells and components.
Most aluminum is made by the Hall-Heroult process comprising electrolysis of alumina in a molten cryolite bath using carbon anodes and cathodes. The aluminum settles under the cryolite bath on the carbon cathode. However, the aluminum does not wet the carbon cathode and electromagnetic forces in the cell produce waves in and the humping of the molten aluminum. To ensure that the carbon cathode floor of the cell is always completely covered with aluminum, a relatively thick cathode layer, pad or pool of aluminum is maintained, which continues to be subject to waving and humping movement. The latter factor necessitates substantial anode-cathode spacing or gap to avoid shorting between the anode and the moving aluminum cathode pool. It is that spacing or gap that causes considerable electrical energy loss in the resistance heating of the cryolite-aluminum cell bath therein.
Various cell designs of drained cathodes and of cathode pool packing, baffles or weirs have been proposed to alleviate the aluminum movement and energy problem. Also, various aluminum-wettable materials and bodies have been proposed without much success for economically accomodating cell designs that can alleviate those problems. There remains the basic need for cathodes and cathode pool structures of aluminum wettable, durable bodies which can be readily and economically fabricated.